Capacitive touch sensors are susceptible to manufacturing defects, wear and breakage over the life of the end product. Changes in the capacitive properties of a panel from those used during development or over the life of the project can impair performance or create a defective interface. Previous methods for determining the manufacturing quality of a capacitive touch panel included optically scanning the panel for defects and physically, mechanically engaging the panel. Mechanical detection of defects is low and requires precision robotic test equipment. Optical scanning is prone to mistakes and good panels can be rejected as falsely defective and defective panels can be falsely passed as good.
Other fault detection methods rely on external circuitry, mechanical test structures and different methods relative to the sensing method to determine and locate faults. Such methods increase system complexity and add additional failure mechanisms in the system test, which decreases reliability of the tests and increases costs for production through decreased yield.